1. Field of the Invention
The present disclosure relates to switching circuits and methods of testing thereof.
2. Description of the Prior Art
Often, switching circuits include several switching devices connected in parallel with one another whereby the current capacity of the switching circuit is the sum of the capacities of each switching device. This is particularly useful for applications in which the power required by the load exceeds the capacity of a single switching device. One example of such switching circuits is found in aircraft power distribution systems, wherein for example eight solid-state switching devices may be provided in parallel. Generally, the switching devices can fail open or closed. Each switching device has a driver which can be the cause of the failure. If one or more of the switching devices fails open the others can act as backup switches, but potentially may be subjected to current overload. If one or more of the switching devices fails closed, it would not be possible to switch off the switching circuit and it would be readily apparent that such a failure had occurred. If failed open, the failure may be undetectable. Solid-state switching devices are tested thoroughly at the manufacturing stage, but it is desirable to be able to test them in service to ensure that they remain fully functional. This is also known as a built-in-test (BIT).